1. Field of the Invention
The present invention relates to an apparatus and method for adjusting parameters of impedance control based on information of a force sensor provided for an end effector of an industrial robot.
The impedance control denotes a control on a position and a force for setting mechanical impedances (inertia, damping coefficient, and rigidity) which are generated in the case where a force is applied from the outside to the end of a robot to values convenient to a target work.
2. Discussion of the Background
There is a widely known technique that, in the case of executing a contact work such as mating by using an industrial robot, a force sensor is attached to an end effector or a wrist part of a robot manipulator, and force control using information of the force sensor is performed. As a force control method, for example, impedance control is easily used.
In the impedance control, feedback control is performed so that a response of a position when an external force acts on an end effector is obtained according to desired inertia, viscosity, and rigidity characteristics. By the control, a force generated when workpieces (objects to be worked) come into contact with each other at the time of a mating operation is passed off, and a positional error can be absorbed. However, if the parameters such as inertia, viscosity, and rigidity are improper, it may take an extremely long time to execute the operation. There is a case that a control system becomes unstable (oscillates) at the time of contact and the operation cannot be performed. Consequently, the parameters of the impedance control have to be properly adjusted.
Japanese Unexamined Patent Application Publication No. 2001-277162 discloses a technique of adjusting parameters of the impedance control.
In the publication, an adjustment worker (teacher) adjusts behavior designation parameters of weight (heavy and light) and hardness (hard and soft) by a button operation while recognizing a force response on a display unit and, based on the behavior designation parameters, adjusts impedance parameters by the fuzzy inference.